Arrangement for converting acoustic energy into electrical energy



June 21 1927 A. MEI5$NER1-:-

ARRANGEMENT FOR CONVERTING ACOUSTIC ENERGY INTO ELECTRICAL ENERGY FiledMay 29, 1924 lNVENTOR ALEXANDER MHSSN ER 59 &%

ATTORNEY Patented June 21; 1 927.

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Application filed Kay 29, 1e24, Serial n.

My inventionrelates to arrangements for converting acoustic energy intoelectrical energy by meansof piezo-electric crystals.

An ob ect of the invention is to provide a device which will convertsound wavesinto electric waves without distortion. v p

Another object is to provide an arrangement whereby theindividuabefi'ectsof sepa rate sources of sound'may be combined tooperate any sound receiving device,'the relative intensities of theseparate sources being separately controlled in their effects on thesound receiving device.

Other objects will be app rent fronr the following description andclaims when considered with the accompanying drawing, in which: Y

Fig. 1 shows a circuit embodying. one form of my invention.

Fig. 2 shows a circuit embodying a modification; I

The so-called piezo-electric crystals have, as known, the property ofreacting upon mechanical shocks by freeing electric charges and therebygenerating an (M. F.

According to the" present invention this phenomenon is used in such-away that when the crystal is fastened to a sound-board of a musicalinstrument, the charges becoming ,free in the rhythm of the acousticvibrations are directly led to the input (grid-cathode) of anincandescent cathode tube. The platefilament current of this vacuum tubethen fluctuates in the same sense as the grid volta c. This arrangementrepresents a means 0 converting acoustic energy into electrical energy.A great advantage of this or stal-- microphoneas compared with the usuacarbon microphone is that the sounds are re produced without distortion.Fig. 1 of the annexed drawing shows an exam le ofthe new arrangements isa sound board, for instance of a violin. K- is the crystal.provided'with two metal coatings, V is an amplifying vacuum tubeWhlCll, for instance, contains the primary of a transformer C in theplate-filament circuit. Connected to the secondary of transformer C istelephone T. p p

In order to reproduce orchestral music, one or more crystals may befastened to the different musical instruments and the separateamplifications can be regulated iii 1 3. and; In, scra -y m 2 1925.

a waythat themusic is correctly reproduced. A clrcult for accomplishingthis result'is illustrated in. Fig. 2. R B R and R are v the soundboards or sound responsive 'portions of the different musicalinstruments. Mounted on each of the sound boards'B R R isa crystal K Kand K respectively.

In order to increase the effect of one sound board, several crystals maybe fastened to the same sound board. Sound board R has two crystals K',and'K fastened to it.

Eac nected to'the-inpu't circuit of aseparate' am. pl1fiei tube V V V,,-,V and V .respectively and the output of each ofthese tubes;

connected'to the 'rimary of a separat'e'transformer' C (3,, C and (3respectively, Thesecondaries, of: these transformers are connected inseries with a telepholie T, so that their joint effects will beimpressed-on the telephone T. Care should 'be'taken that thetransformers are connectedfso that or sta'ls K and K mounted on the addin their effects. If instead of the sound board a suitable membrane isused, tliis arrangement canbe employed for the same microphone is taken.4

Having described my invention, what I claim is:

1. A device for converting sound waves into electricalv impulseundulations, which comprlses a plurality of piezo-electric bodiespurposes as ordinary crystal K K K,,,'K,, and K isfcon? 7 same soundcard adapted to produce electrical impulse undu- 5 latio'ns, inaccordance-with the variation in: pressure exerted thereon, meansassociated f with certain of said bodies adapted to produce,YfllllltlODS in pressure on certain of said bodles in; response tosound waves, means associated with certain others of the saidpiezo-electr'ic bodies adapted to produce vw r'iations in,p'ressureonsaid last mentioned bodies, am jlifyin means associated with said lezo-eectricio v der t e'se arate outputs of the several amfilifiers a itive."

2. A device for converting sound'fwaves;

into electrical undulations comprising in combination, a luralit ments;a; piezo-e ectric ody associated with each of said instruments and be ad to generate electrical undulations inaccorddies, and meansto re'nofmusical .instru- 5 ance with the output of said instruments,

separate amplifying means connected to each of said piezoectric bodies,and a reproducer adapted tobe actuated by said, ampli struments adaptedto produce mechanical vibrations, a

iezo-electric body connected to each of said instruments and adapted tobe vibrated by said mechanical vibrations and being also adapted togenerate electrical undulations in accordance with the vibrations of thepiezo-electric bodies, means to amplify said electrical undulations andmeans to combine said amplified undulations.

4. In a device for converting acoustical impulses into electricalundulations the combination, of a musical instrument adapted to producemechanical vibrations, a plurality of piezo-electric bodies connected tosaid instrument and adapted to be vibrated by the vibrations of saidinstrument, to produce electrical undulations connected to a separateamplifier each of said bodies adapted to amplify the electricalundulations produced thereby, and means whereby said amplified impulsesmay be added together.

5. In a devicelfor converting acoustical impulses into electricalundu1ations,'the combination of a sound producing member having avibratorye'lement, a plurality of piezoelectric bodies connected to saidelement and adapted to be vibrated by said element to produce electricalundulations, a separate amplifier connected With each of said bodies,adapted to amplify said electrical undulations and means whereby saidamplifiedundulations may be added together.

6. A device for converting sound waves into electrical undulationscomprising in combination, a plurality of sound producing members eachhaving a vibratoryele ment, a piezo electric body associated with eachof said elements and being adapted to generate electrical undulations inaccordance with the vibration of said elements, separate amplifyingmeans connected to each of said piezo-electric bodies, and a reproduceradapted to be actuated by said amplifiers.

ALEXANDER MEISSNER.

